Back Priming Cedar Siding

It is strongly recommended that you go with the two coat system for protecting your cedar siding.

Back priming cedar siding.

All siding takes on seasonal moisture from sources as diverse as direct rain wicking and vapor diffusion through the wall assembly. Back priming natural wood siding helps control rotting mold build up cupping and movement in the wood ultimately giving your siding and your stain finish more longevity. Priming western red cedar helps the wood s natural properties stay put. What that means is that you can put primer on the cedar siding but brown stains will come through.

The only way to block the tannins in the cedar siding is to use an oil primer. Back priming consists of applying a coat of primer to the reverse side and edges of boards before installing. Importance of back priming when installing wood siding. Without a primer tannins from within the cedar mix with moisture and seep to the wood s surface naturally staining and discoloring the surface.

When back priming be sure to prime the ends of each piece after it has been cut to fit since end grain will absorb the most moisture. Back priming helps prevent paint from peeling by reducing the amount of water vapor that passes through the wood. You have to use oil primers on cedar siding. Although intended primarily for restoring horizontal wood surfaces such as decks these products generally work almost as well on vertical surfaces.

Regardless of vapor barriers they don t help the siding itself. Not only does back priming prevent rot it prevents bowing cupping. Prime all sides and end grains or cuts before installation. It occurs either when heated or air conditioned air from the house radiates out and meets the cold or hot outside air.

Prime the cedar before you paint it. This is called extractive bleeding a naturally occurring process that does not affect western red cedar s properties. A primer with a paint top coat will have a significantly longer service life than will a single coat of paint or even a solid stain. Backpriming prevents rotting by sealing the rear side of the wood that is exposed to all the moisture coming out of vapor barriers.

These are tannins from cedar wood leaking through a water based primer.